The invention relates to a saw blade for a circular saw, which is designed as a circular disc provided with a radius and a thickness, and also with teeth being arranged on the circumference of the circular disc, and air passage openings in the form of elongate holes being arranged in its essentially circular side faces. A saw blade of this kind is intended, in particular, for use with a circular saw having two parallel saw blades that can be driven coaxially in mutually opposite directions of rotation.
A saw blade of this kind is known, for example, from International Patent Application WO 97/13609. In this application, air passage openings in the form of elongate holes that are aligned essentially radially and extend as far as the centre of rotation of the saw blade, in particular openings that are approximately banana-shaped in cross section, are described in the saw blade (to prevent magnetization).
A saw blade of the type described at the outset is preferably suitable for use for a circular saw with two parallel saw blades that can be driven coaxially in mutually opposite directions of rotation, as proposed in German Utility Model Application DE 298 04 220.7. As regards further possible details and embodiments of a circular saw of this kind and of a saw blade according to the invention that are not described below, attention is drawn to this application in its entirety.
According to this German utility model application, low-wear and trouble-free operation is ensured for a cutting device, in particular for a circular saw of the type stated at the outset here, by structurally simple and low-cost measures. This is achieved by mechanical holding means for the cutting elements (saw blades) of a design such that a gap that prevents friction is necessarily guaranteed between the cutting elements in the assembled state. This eliminates the need to produce a pressure cushion between the saw blades. The gap is ensured purely by the mechanical mounting of the saw blades, the holding means being designed in such a way, expediently being adapted to the dimensions, in particular the thickness, of the saw blades, that the gap between the cutting elements in the assembled statexe2x80x94especially in the region of teeth arranged on the outer circumferencexe2x80x94has a clear width in a range of at least {fraction (2/100)} mm to at most about {fraction (1/10)} mm. Such a clearance, on the one hand, ensures that there is virtually no friction between the cutting elements even during operation and, on the other hand, avoids a situation where pieces of material (chips) removed during the cutting operation might force themselves between the saw blades and then push them apart, by a wedging effect.
Neither the saw blade described in International Patent Application WO 97/13609 nor that described in German Utility Model Application DE 298 04 220.7 is ideal as regards dissipation of the heat that arises during the cutting operation. Another disadvantage with the known saw blade with the radial slots is that, in the case of a firmly clamped saw blade, its stability is reduced by the slots.
The object on which the invention is based is to improve a saw blade of the type stated at the outset in terms of its running behaviour, taking into account, in particular, its thermal characteristics, while ensuring high mechanical stability.
According to the invention, this is achieved by a saw blade of the type stated at the outset in which a respective longitudinal extent of the air passage openings in the form of elongate holes extends in a direction that lies within a range that extends from a direction of extension of a secant through the side faces to the direction of extension of a circumferential arc in the side faces, the air passage openings in the form of elongate holes lying in an outer region formed by an annular area, the outer boundary of which is formed by the circumference of a circle with a radius of the order of about 0.75 to 0.95 times the radius of the circular disc, and the inner boundary of which is formed by the circumference of a circle whose radius is half that of the circular disc.
Such a saw blade advantageously has, on the one hand, a high stability since the air passage openings do not reduce this, and, on the other hand, it has enhanced running properties thanks to optimized dissipation of the heat that arises during sawing.
The saw blade according to the invention is particularly efficient if the air passage openings in the form of elongate holes extend essentially in a direction parallel to the circumference, i.e. intersect the radius of the circular disc at a right angle. Moreover, it is advantageous, in particular, if the inner boundary is formed by the circumference of a circle with a radius that is two-thirds the size of the radius of the circular disc. By virtue of this embodiment, the majority of the heat that arises is dissipated in the very location in which it arises, and any significant conduction of heat into the certre of rotation of the saw blade is prevented.
Further advantageous embodiment features of the invention are set forth below in the following description.